Numerical Simulation And Optimization On Multiphase Flow And Flocculation, Sedimentation In The Red Mud Thickener

ABSTRACT:A deep cone red mud thickener is targeted and modelled, based on appropriate and reasonable simplification and assumptions, the article coupled the PBM population balance model to computational fluid dynamics, with Euler-Euler two-phase flow model and Realizablek-ε turbulence model, the physical and mathematical model have been established, and completed the unsteady simulation of red mud particles flocculation and sedimentation processes in the feedwell. Finally many factors including solids concentration distributions are analyzed and discussed, the residence time distribution, intensity distribution of the turbulent kinetic energy and the particle size distribution of red mud. By means of the univariate analysis of parameters which affect the distribution of solids in the red mud thickener and flocculation and sedimentation processes, such as feed flow rate, feed solid concentration, feed red mud particle size and flocculants add location, the article realized the impact law of these factors on red mud thickener flocculation and sedimentation processes. Besides, the article finished the multivariate multi-index optimization analysis and got the influence weight and optimal combination of the process parameters of the red mud thickener by applying the orthogonal experimental design method as well as the means of matrix analysis. The main conclusions are as follows:(1) Through reasonable simplification and assumption, the article established the mathematical physics solving model of the red mud thickener multiphase flow and red mud flocculation and sedimentation process, completed the mesh independent and time-step independence check and verified the reliability of the mathematical models, which is based on appropriate grid number,time step and the industrial production data.(2) Single factor impact analysis shows that:in a certain range of feed flow rate, feed raw red mud particle size and feed solid concentration, the larger the parameters are and the more forward position the flocculants is added, the more conducive to improve the feedwell’s solids distribution,flocculant’s flocculation efficiency and the red mud particles’flocculation and sedimentation.(3) Using orthogonal test design method, combining with matrix analysis’multivariate multi-index optimization analysis, the results show that:the process parameters’combination of optimization program of the flocculation and sedimentation of red mud thickener are:feed flow rate1900m3/h, feed solid concentration120g/L, the distance from the feed inlet position flocculants add points to7m, the feed particle size of red mud is diaspore bauxite. Primary and secondary effects of each order to optimize the process parameters is BCAD, namely, the greatest impact is feed solids (47.12%), followed by feed particle size of red mud (23.50%), the relatively weak parameter is position of flocculants added (16.30%) and feed flow is the weakest (13.08%).